package LinkedList;

import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 殇
 * Date: 2025-07-25
 * Time: 17:03
 */
public class MyLinkedList {

    static class ListNode{
        int val;
        ListNode prev;
        ListNode next;

        public ListNode(int val) {
            this.val=val;
        }

    }

    public ListNode head;
    public ListNode tail;
    //头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
            tail=node;
        }
        else{
            node.next=head;
            head.prev=node;
            head=node;
        }
    }

    //尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=tail=node;
        }
        else{
            node.prev=tail;
            tail.next=node;
            tail=node;
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        ListNode node=new ListNode(data);
        if(index<0||index>size()){
            System.out.println("下标不合法");
            return ;
        }
        if(index==0){
            addFirst(data);
            return ;
        }
        if(index==size()){
            addLast(data);
            return ;
        }
        ListNode cur=head;
        while(cur!=null){
            index--;
            if(index==0){
                node.next=cur;
                node.prev=cur.prev;
                cur.prev=node;
                node.prev.next=node;
            }
        }
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }

    public ListNode search(int index){
        if(index<0){
            return null;
        }
        ListNode cur=head;
        int count=0;
        while(cur!=null){
            count++;
            if(count==index){
                return cur;
            }
            cur=cur.next;
        }
        return null;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    if(head == null) {
                        //只有一个节点的情况下
                        tail = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    //删除中间和尾巴
                    if(cur.next == null) {
                        //尾巴
                        cur.prev.next = cur.next;
                        tail = tail.prev;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    if(head == null) {
                        //只有一个节点的情况下
                        tail = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    //删除中间和尾巴
                    if(cur.next == null) {
                        //尾巴
                        cur.prev.next = cur.next;
                        tail = tail.prev;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }
                }
                //return;
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        ListNode cur=head;
        int count=0;
        while(cur!=null){
            count++;
            cur=cur.next;
        }
        return count;
    }
    public void display(){
        ListNode cur=head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
    }
    public void clear(){
        head.next=head.prev=null;
    }
}
